Human skin offers a protective barrier against environmental mechanical damage thanks to the reversible deformability of its structure. In particular, the dermal extracellular matrix (ECM) ensures an essential role in skin cohesion and influences biomechanical properties of the skin.
More specifically, elastic fibre s represent the primary effectors of skin elasticity due to their key role in skin compliance and resilience[4,5].
The organised arrangement of the elastic fibre network is more important than the abundance per se of fibres, as regards the impact on the functionality of elastic fibres and thus the resulting biomechanical properties of the skin[6].
In vitro 3D skin models are powerful and predictive tools for the screening and efficacy testing of bioactive molecules[1]. Such models use artificial, synthetic or bio-based extracellular matrices to provide a cell-adhesive substrate to cell suspensions and guide the three-dimensional organisation[2].
Although exogenous scaffolds have played a critical role in tissue reconstruction, they create a bias when measuring the biomechanical properties of bioengineered tissues like human skin[3].
3D scaffold-free microtissues use the ability of cells to aggregate, adhere, proliferate, create cell-to-cell interactions, secrete their own endogenous ECM and ultimately produce their own architecture and microenvironment in a non-adhesive environment[7].
These bioengineered spheroid microtissues, obtained using cells only, in the absence of artificial ECM scaffolds, are increasingly used as research tools for investigating cell-matrix interactions, cell-to-cell communication, as well as for safety and efficacy testing[8-11].
However, such models have not been used yet to assess the biomechanical properties of skin-derived bioengineered tissues.
In this study, we developed and characterised a 3D scaffold-free spheroid microtissue, exclusively composed of normal human dermal fibroblasts (NHDF) to mitigate bias in the in vitro evaluation of dermal elastic properties.
For this, we studied the elastic fibre network within microtissues cultured for eight and 15 days using two-photon autofluorescence (2PAF) imaging and we evaluated tissue stiffness at the nanoscale using atomic force microscopy (AFM).
This new advanced 3D model has been successfully used to measure the efficacy of EleVastin, a novel active ingredient developed by Gattefossé, fighting against age related loss of skin elasticity.